This is a traditional way to knit any size muffler (winter neck scarf). All you do, using any size needles and any size wool or yarn. is to cast on till you have the width you want. And then you simply knit every row (garter stitch) till it is as long as it needs to be.
This is a good way to make use of left over wool or yarn by working in stripes.
The finished scarf looks nice if the first stitch of each row is slipped rather than knit. Or you can knit the first stitch and slip the second at the beginning of each row.
Fringe is optional.